Struts2源码阅读(三)_Dispatcher&ConfigurationProvider

首先强调一下struts2的线程程安全，在Struts2中大量采用ThreadLocal线程局部变量的方法来保证线程的安全,像Dispatcher等都是通过ThreadLocal来保存变量值,使得每个线程都有自己独立的实例变量,互不相干.

 

接下来就从Dispatcher开始看起，先看其构造函数：

 

//创建Dispatcher，此类是一个Delegate，它是真正完成根据url解析转向，读取对应Action的地方
    public Dispatcher(ServletContext servletContext, Map<String, String> initParams) {
        this.servletContext = servletContext;
        //配置在web.xml中的param参数
        this.initParams = initParams;
    }

//创建Dispatcher，此类是一个Delegate，它是真正完成根据url解析转向，读取对应Action的地方 public Dispatcher(ServletContext servletContext, Map<String, String> initParams) { this.servletContext = servletContext; //配置在web.xml中的param参数 this.initParams = initParams; }

 

我们再看在FilterDispatcher创建Dispatcher的:

 

protected Dispatcher createDispatcher(FilterConfig filterConfig) {
    Map<String, String> params = new HashMap<String, String>();
    for (Enumeration e = filterConfig.getInitParameterNames(); e.hasMoreElements();) {
        String name = (String) e.nextElement();
        String value = filterConfig.getInitParameter(name);
        params.put(name, value);
    }
都可以从FilterConfig中得到
    return new Dispatcher(filterConfig.getServletContext(), params);
}

protected Dispatcher createDispatcher(FilterConfig filterConfig) { Map<String, String> params = new HashMap<String, String>(); for (Enumeration e = filterConfig.getInitParameterNames(); e.hasMoreElements();) { String name = (String) e.nextElement(); String value = filterConfig.getInitParameter(name); params.put(name, value); } 都可以从FilterConfig中得到 return new Dispatcher(filterConfig.getServletContext(), params); }

 

分七步载入各种配置属性,都是通过ConfigurationProvider接口进行的,这个接口提供init(),destroy(),register()等方法.
将各种ConfigurationProvider初始化之后将实例添加到ConfigurationManager的List里面.
最后通过循环调用List里的这些destroy(),register()等方法实现对配置文件的属性进行注册和销毁等功能.
下面将分析这七层功夫是怎样一步步练成的.

 

首先是init_DefaultProperties()

创建Dispatcher之后,来看init()方法
init()方法是用来Load用户配置文件,资源文件以及默认的配置文件.

主要分七步走,看下面注释

 

public void init() {

    if (configurationManager == null) {
    //设置ConfigurationManager的defaultFrameworkBeanName.
    //这里DEFAULT_BEAN_NAME为struts,这是xwork框架的内容,Framework可以是xwork,struts,webwork等
        configurationManager = new ConfigurationManager(BeanSelectionProvider.DEFAULT_BEAN_NAME);
    }
      //读取properties信息,默认的default.properties,
    init_DefaultProperties(); // [1]
//读取xml配置文件
      init_TraditionalXmlConfigurations(); // [2]
//读取用户自定义的struts.properties
      init_LegacyStrutsProperties(); // [3]
//自定义的configProviders
      init_CustomConfigurationProviders(); // [5]
//载入FilterDispatcher传进来的initParams
      init_FilterInitParameters() ; // [6]
//将配置文件中的bean与具体的类映射
      init_AliasStandardObjects() ; // [7]

//构建一个用于依赖注射的Container对象
//在这里面会循环调用上面七个ConfigurationProvider的register方法
//其中的重点就是DefaultConfiguration的#reload()方法
      Container container = init_PreloadConfiguration();
      container.inject(this);
      init_CheckConfigurationReloading(container);
      init_CheckWebLogicWorkaround(container);

      if (!dispatcherListeners.isEmpty()) {
          for (DispatcherListener l : dispatcherListeners) {
              l.dispatcherInitialized(this);
          }
      }
  }

public void init() { if (configurationManager == null) { //设置ConfigurationManager的defaultFrameworkBeanName. //这里DEFAULT_BEAN_NAME为struts,这是xwork框架的内容,Framework可以是xwork,struts,webwork等 configurationManager = new ConfigurationManager(BeanSelectionProvider.DEFAULT_BEAN_NAME); } //读取properties信息,默认的default.properties, init_DefaultProperties(); // [1] //读取xml配置文件 init_TraditionalXmlConfigurations(); // [2] //读取用户自定义的struts.properties init_LegacyStrutsProperties(); // [3] //自定义的configProviders init_CustomConfigurationProviders(); // [5] //载入FilterDispatcher传进来的initParams init_FilterInitParameters() ; // [6] //将配置文件中的bean与具体的类映射 init_AliasStandardObjects() ; // [7] //构建一个用于依赖注射的Container对象 //在这里面会循环调用上面七个ConfigurationProvider的register方法 //其中的重点就是DefaultConfiguration的#reload()方法 Container container = init_PreloadConfiguration(); container.inject(this); init_CheckConfigurationReloading(container); init_CheckWebLogicWorkaround(container); if (!dispatcherListeners.isEmpty()) { for (DispatcherListener l : dispatcherListeners) { l.dispatcherInitialized(this); } } }

 

分七步载入各种配置属性,都是通过ConfigurationProvider接口进行的,这个接口提供init(),destroy(),register()等方法.
将各种ConfigurationProvider初始化之后将实例添加到ConfigurationManager的List里面.
最后通过循环调用List里的这些destroy(),register()等方法实现对配置文件的属性进行注册和销毁等功能.
下面将分析这七层功夫是怎样一步步练成的.

 

首先是init_DefaultProperties()

 

private void init_DefaultProperties() {
    configurationManager.addConfigurationProvider(new DefaultPropertiesProvider());
}
接来看DefaultPropertiesProvider好了,DefaultPropertiesProvider实际上只是实现了register()方法
public void register(ContainerBuilder builder, LocatableProperties props)
        throws ConfigurationException {

    Settings defaultSettings = null;
    try {
        defaultSettings = new PropertiesSettings("org/apache/struts2/default");
    } catch (Exception e) {
        throw new ConfigurationException("Could not find or error in org/apache/struts2/default.properties", e);
    }

    loadSettings(props, defaultSettings);
}

private void init_DefaultProperties() { configurationManager.addConfigurationProvider(new DefaultPropertiesProvider()); } 接来看DefaultPropertiesProvider好了,DefaultPropertiesProvider实际上只是实现了register()方法 public void register(ContainerBuilder builder, LocatableProperties props) throws ConfigurationException { Settings defaultSettings = null; try { defaultSettings = new PropertiesSettings("org/apache/struts2/default"); } catch (Exception e) { throw new ConfigurationException("Could not find or error in org/apache/struts2/default.properties", e); } loadSettings(props, defaultSettings); }  

 

 

//PropertiesSettings构造方法
    //读取org/apache/struts2/default.properties的配置信息，如果项目中需要覆盖，可以在classpath里的struts.properties里覆写
    public PropertiesSettings(String name) {

        URL settingsUrl = ClassLoaderUtils.getResource(name + ".properties", getClass());

        if (settingsUrl == null) {
            LOG.debug(name + ".properties missing");
            settings = new LocatableProperties();
            return;
        }

        settings = new LocatableProperties(new LocationImpl(null, settingsUrl.toString()));

        // Load settings
        InputStream in = null;
        try {
            in = settingsUrl.openStream();
            settings.load(in);
        } catch (IOException e) {
            throw new StrutsException("Could not load " + name + ".properties:" + e, e);
        } finally {
            if(in != null) {
                try {
                    in.close();
                } catch(IOException io) {
                    LOG.warn("Unable to close input stream", io);
                }
            }
        }
    }

    //loadSettings主要是将progerty的value和Locale从上面PropertiesSettings中取得并存放到LocatableProperties props
    //这个props是register的一个入参.
    protected void loadSettings(LocatableProperties props, final Settings settings) {
        // We are calling the impl methods to get around the single instance of Settings that is expected
        for (Iterator i = settings.listImpl(); i.hasNext(); ) {
            String name = (String) i.next();
            props.setProperty(name, settings.getImpl(name), settings.getLocationImpl(name));
        }
    }

//PropertiesSettings构造方法 //读取org/apache/struts2/default.properties的配置信息，如果项目中需要覆盖，可以在classpath里的struts.properties里覆写 public PropertiesSettings(String name) { URL settingsUrl = ClassLoaderUtils.getResource(name + ".properties", getClass()); if (settingsUrl == null) { LOG.debug(name + ".properties missing"); settings = new LocatableProperties(); return; } settings = new LocatableProperties(new LocationImpl(null, settingsUrl.toString())); // Load settings InputStream in = null; try { in = settingsUrl.openStream(); settings.load(in); } catch (IOException e) { throw new StrutsException("Could not load " + name + ".properties:" + e, e); } finally { if(in != null) { try { in.close(); } catch(IOException io) { LOG.warn("Unable to close input stream", io); } } } } //loadSettings主要是将progerty的value和Locale从上面PropertiesSettings中取得并存放到LocatableProperties props //这个props是register的一个入参. protected void loadSettings(LocatableProperties props, final Settings settings) { // We are calling the impl methods to get around the single instance of Settings that is expected for (Iterator i = settings.listImpl(); i.hasNext(); ) { String name = (String) i.next(); props.setProperty(name, settings.getImpl(name), settings.getLocationImpl(name)); } } 

 

再来看第二步：init_TraditionalXmlConfigurations() 

 

private void init_TraditionalXmlConfigurations() {
 //首先读取web.xml中的config初始参数值
    //如果没有配置就使用默认的DEFAULT_CONFIGURATION_PATHS:"struts-default.xml,struts-plugin.xml,struts.xml"，
    //这儿就可以看出为什么默认的配置文件必须取名为这三个名称了
    //如果不想使用默认的名称，直接在web.xml中配置config初始参数即可
    String configPaths = initParams.get("config");
    if (configPaths == null) {
        configPaths = DEFAULT_CONFIGURATION_PATHS;
    }
    String[] files = configPaths.split("//s*[,]//s*");
    for (String file : files) {
        if (file.endsWith(".xml")) {
            if ("xwork.xml".equals(file)) {
    //XmlConfigurationProvider负责解析xwork.xml
                configurationManager.addConfigurationProvider(new XmlConfigurationProvider(file, false));
            } else {
    //其它xml都是由StrutsXmlConfigurationProvider来解析
                configurationManager.addConfigurationProvider(new StrutsXmlConfigurationProvider(file, false, servletContext));
            }
        } else {
            throw new IllegalArgumentException("Invalid configuration file name");
        }
    }
}

private void init_TraditionalXmlConfigurations() { //首先读取web.xml中的config初始参数值 //如果没有配置就使用默认的DEFAULT_CONFIGURATION_PATHS:"struts-default.xml,struts-plugin.xml,struts.xml"， //这儿就可以看出为什么默认的配置文件必须取名为这三个名称了 //如果不想使用默认的名称，直接在web.xml中配置config初始参数即可 String configPaths = initParams.get("config"); if (configPaths == null) { configPaths = DEFAULT_CONFIGURATION_PATHS; } String[] files = configPaths.split("//s*[,]//s*"); for (String file : files) { if (file.endsWith(".xml")) { if ("xwork.xml".equals(file)) { //XmlConfigurationProvider负责解析xwork.xml configurationManager.addConfigurationProvider(new XmlConfigurationProvider(file, false)); } else { //其它xml都是由StrutsXmlConfigurationProvider来解析 configurationManager.addConfigurationProvider(new StrutsXmlConfigurationProvider(file, false, servletContext)); } } else { throw new IllegalArgumentException("Invalid configuration file name"); } } }  

 

对于其它配置文件只用StrutsXmlConfigurationProvider，此类继承XmlConfigurationProvider，而XmlConfigurationProvider又实现ConfigurationProvider接口。
类XmlConfigurationProvider负责配置文件的读取和解析，
首先通过init()中的loadDocuments(configFileName);利用DomHelper中的
public static Document parse(InputSource inputSource, Map<String, String> dtdMappings) 将configFileName配置文件通过SAX解析方式按照DtdMappings解析成Document对象.
然后通过Provider的register()方法加载"bean"和"constant"属性,再通过loadPackages()加载package及package中的属性
addAction()方法负责读取<action>标签，并将数据保存在ActionConfig中；
addResultTypes()方法负责将<result-type>标签转化为ResultTypeConfig对象；
loadInterceptors()方法负责将<interceptor>标签转化为InterceptorConfi对象；
loadInterceptorStack()方法负责将<interceptor-ref>标签转化为InterceptorStackConfig对象；
loadInterceptorStacks()方法负责将<interceptor-stack>标签转化成InterceptorStackConfig对象。
而上面的方法最终会被addPackage()方法调用,addPackage又会被Provider的loadPackages()调用，将所读取到的数据汇集到PackageConfig对象中。

 

protected PackageConfig addPackage(Element packageElement) throws ConfigurationException {
     PackageConfig.Builder newPackage = buildPackageContext(packageElement);

     if (newPackage.isNeedsRefresh()) {
         return newPackage.build();
     }
     // add result types (and default result) to this package
     addResultTypes(newPackage, packageElement);
     // load the interceptors and interceptor stacks for this package
     loadInterceptors(newPackage, packageElement);
     // load the default interceptor reference for this package
     loadDefaultInterceptorRef(newPackage, packageElement);
     // load the default class ref for this package
     loadDefaultClassRef(newPackage, packageElement);
     // load the global result list for this package
     loadGlobalResults(newPackage, packageElement);
     // load the global exception handler list for this package
     loadGobalExceptionMappings(newPackage, packageElement);
     // get actions
     NodeList actionList = packageElement.getElementsByTagName("action");
     for (int i = 0; i < actionList.getLength(); i++) {
         Element actionElement = (Element) actionList.item(i);
         addAction(actionElement, newPackage);
     }
     // load the default action reference for this package
     loadDefaultActionRef(newPackage, packageElement);
     PackageConfig cfg = newPackage.build();
     configuration.addPackageConfig(cfg.getName(), cfg);
     return cfg;
 }

loadConfigurationFiles解析读取xml中的内容
 private List<Document> loadConfigurationFiles(String fileName, Element includeElement) {
   ...
//通过DomHelper调用SAX进行解析xml
doc = DomHelper.parse(in, dtdMappings);
...
   Element rootElement = doc.getDocumentElement();
   NodeList children = rootElement.getChildNodes();
   int childSize = children.getLength();

   for (int i = 0; i < childSize; i++) {
     Node childNode = children.item(i);

     if (childNode instanceof Element) {
       Element child = (Element) childNode;

       final String nodeName = child.getNodeName();

       if ("include".equals(nodeName)) {
         String includeFileName = child.getAttribute("file");

      //解析每个action配置是，对于include文件可以使用通配符*来进行配置
         //如Struts.xml中可配置成<include file="actions_*.xml"/>
         if (includeFileName.indexOf('*') != -1) {
           ClassPathFinder wildcardFinder = new ClassPathFinder();
           wildcardFinder.setPattern(includeFileName);
           Vector<String> wildcardMatches = wildcardFinder.findMatches();
           for (String match : wildcardMatches) {
       //递归Load子file中的<include/>
             docs.addAll(loadConfigurationFiles(match, child));
           }
         } else {

           docs.addAll(loadConfigurationFiles(includeFileName, child));
         }
       }
     }
   }
   docs.add(doc);
   loadedFileUrls.add(url.toString());
   ...
   return docs;
 }

protected PackageConfig addPackage(Element packageElement) throws ConfigurationException { PackageConfig.Builder newPackage = buildPackageContext(packageElement); if (newPackage.isNeedsRefresh()) { return newPackage.build(); } // add result types (and default result) to this package addResultTypes(newPackage, packageElement); // load the interceptors and interceptor stacks for this package loadInterceptors(newPackage, packageElement); // load the default interceptor reference for this package loadDefaultInterceptorRef(newPackage, packageElement); // load the default class ref for this package loadDefaultClassRef(newPackage, packageElement); // load the global result list for this package loadGlobalResults(newPackage, packageElement); // load the global exception handler list for this package loadGobalExceptionMappings(newPackage, packageElement); // get actions NodeList actionList = packageElement.getElementsByTagName("action"); for (int i = 0; i < actionList.getLength(); i++) { Element actionElement = (Element) actionList.item(i); addAction(actionElement, newPackage); } // load the default action reference for this package loadDefaultActionRef(newPackage, packageElement); PackageConfig cfg = newPackage.build(); configuration.addPackageConfig(cfg.getName(), cfg); return cfg; } loadConfigurationFiles解析读取xml中的内容 private List<Document> loadConfigurationFiles(String fileName, Element includeElement) { ... //通过DomHelper调用SAX进行解析xml doc = DomHelper.parse(in, dtdMappings); ... Element rootElement = doc.getDocumentElement(); NodeList children = rootElement.getChildNodes(); int childSize = children.getLength(); for (int i = 0; i < childSize; i++) { Node childNode = children.item(i); if (childNode instanceof Element) { Element child = (Element) childNode; final String nodeName = child.getNodeName(); if ("include".equals(nodeName)) { String includeFileName = child.getAttribute("file"); //解析每个action配置是，对于include文件可以使用通配符*来进行配置 //如Struts.xml中可配置成<include file="actions_*.xml"/> if (includeFileName.indexOf('*') != -1) { ClassPathFinder wildcardFinder = new ClassPathFinder(); wildcardFinder.setPattern(includeFileName); Vector<String> wildcardMatches = wildcardFinder.findMatches(); for (String match : wildcardMatches) { //递归Load子file中的<include/> docs.addAll(loadConfigurationFiles(match, child)); } } else { docs.addAll(loadConfigurationFiles(includeFileName, child)); } } } } docs.add(doc); loadedFileUrls.add(url.toString()); ... return docs; }  

 

Come From:  http://qidaoxp.javaeye.com/blog/494444